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Thyroglobulin (Tg) is an important tool to evaluate the persistence and recurrence risk in differentiated thyroid cancer (DTC). We aimed to evaluate the correlation between pre-radioiodine therapy stimulated Tg (pre-RAI Tg) levels and the first response to treatment evaluation, and to establish a cut-off pre-RAI Tg threshold for predicting an initial excellent response. Retrospective cohort study of DTC patients who underwent total thyroidectomy and radioiodine therapy. Response to therapy was evaluated 6 to 24 months after initial therapy, and patients were classified as: excellent response (ER); indeterminate response (IndR) and incomplete response (IncR). Total patients: 166 among which 85.5% female with mean age of 47.6 ± 13 years. The ER had a significantly lower pre-RAI Tg in comparison to IndR (p<0.001) and IncR (p<0.001), and pre-RAI Tg were different between the IndR and IncR (p=0.02). A cut-off pre-RAI Tg value at 7.55ng/ml was obtained by receiver operating characteristics curve for differentiating ER from IndR and IncR. The area under curve was 0.832 (95% CI 0.76–0.91). In multivariate analysis, ATA low-risk (RR 1.61, 95% CI 1.06–2.43, p=0.025) and Tg below 7.55ng/ml (RR 2.17, 95% CI 1.52–3.10, p<0.001) were associated with ER. After a median of 7.4-year follow-up, 124 (74.7%) patients were allocated into ER, 22 (13.2%) into IndR, and 20 (12%) into IncR. In conclusion, pre-RAI Tg predicts first evaluation of treatment response. Pre-RAI Tg cut-off was a key predictor of initial excellent response to therapy and may be an important tool in the follow-up of DTC patients. [ABSTRACT FROM AUTHOR]

The clinical outcome of papillary thyroid carcinoma (PTC) patients with an indeterminate response after initial therapy is reported to be intermediate, between incomplete and excellent responses. This study evaluated the outcomes of PTC patients with indeterminate response after initial therapy. It was further determined whether the indeterminate findings predicted outcomes more precisely. Patients were further classified into 3 groups based on risk of structural persistence/recurrence: Tg group : detectable thyroglobulin, negative antithyroglobulin antibody, regardless nonspecific imaging findings; TgAb group : positive antithyroglobulin antibody, regardless thyroglobulin levels and nonspecific imaging findings, and Image group: nonspecific findings on neck ultrasonography or faint uptake in the thyroid bed on whole-body scan, undetectable thyroglobulin and negative antithyroglobulin antibody. Sixty-six patients aged 44.1±12.7 years were studied, of whom 58 (87.9%) were females. All patients underwent total thyroidectomy, and 52 patients (78.8%) received radioiodine. After 5.7 years (P25–75 2.6–9.75 years) of follow-up, most patients (89.4%) were reclassified as having an excellent response or remained in the indeterminate response to therapy. Structural recurrence/persistence disease was detected in 7 (10.6%) patients. The persistence/recurrence rate in groups were as follow: Tg , 2.63%; TgAb , 31.25%; Image , 8.3% (p=0.007). The 10-years disease-free survival rate in the TgAb group was significantly reduced (p=0.022). Our results suggest that patients with PTC and indeterminate response due to positive serum antithyroglobulin antibody have more risk of development of structural disease. These findings suggest a more individualized follow-up strategy for patients with an indeterminate response. [ABSTRACT FROM AUTHOR]

Background: Risk stratification for persistent disease is an important step in pediatric differentiated thyroid cancer (DTC) management. The dynamic risk stratification (DRS) is a well validated system for adults, but not yet for children and adolescents. This study evaluated the DRS as well as other prognostic factors in pediatric DTC. Methods: Patients aged ≤18 years from four DTC tertiary teaching hospitals in Southern Brazil were included. Clinical characteristics were systematically retrieved, and all patients were classified according to the risk-stratification system of the 2015 American Thyroid Association pediatric DTC guidelines (ATA risk) and according to DRS (excellent, indeterminate, biochemical, or structural incomplete responses). Disease status was evaluated after initial therapy and at last follow-up visit. Results: Sixty-six patients aged 14.5 ± 3.0 years were studied of whom 54 (81.8%) were girls and 62 (93.9%) had papillary thyroid carcinomas. Tumor size was 2.3 cm (P25–75 1.6–3.5); 41 (63.1%) had cervical and 18 (27.7%) distant metastasis at diagnosis. All patients underwent total thyroidectomy, and 63 (95.5%) received radioiodine. Patients were classified according to DRS after initial therapy (n = 63) as follows: 21 (33%) excellent, 13 (21%) indeterminate, 6 (9%) biochemical, and 23 (37%) structural incomplete responses. Notably, after six years (P25–75 2.7–10.0), most patients remained in the same category. Interestingly, the cutoff analysis of stimulated postoperative thyroglobulin (sPOTg) through receiver operating characteristic curve showed that the value of 37.8 ng/mL showed 81% sensitivity and 100% specificity to predict an excellent response. Prognostic factors associated with persistent disease in the univariate analysis were TNM, ATA risk, DRS, and sPOTg. Conclusion: DRS after initial therapy and sPOTg are strong predictors of disease outcome and might be helpful for defining follow-up strategies in pediatric DTC. [ABSTRACT FROM AUTHOR]